Frequency selecting switch



April 20, 1948. R. L. WOLFF 5' AL FRE UENCY SELECTING SWITCH Filed July 24, 1944 m m m m ROBERTA. 14 04/ 7 BY W/M/fimj Fag X HTTOZ/VEV.

Patented Apr. 20, 1948 FREQUENCY SELECTING SWITCH Robert L. Woli'l', Milwaukee, and William J. Foy, Thiensville, Wia, assignors to Globe-Union Inc., Milwaukee, Wis., a corporation of Delaware Application July 24, 1944, Serial No. 546,398 4 Claims. (Cl. 174-138) This invention relates to improvements in switches and particularly to switches adapted for .use in circuits susceptible to disturbance by po tential variations between the various parts of the switch structure.

In switches such as are used for example in selectively tuning radio receivers to wave bands of different frequency. space limitations require that a plurality of switches or switching units be mounted closely adjacent to each other. Such switches include metallic parts which serve as a frame for the insulation parts bearing the several elements of the various switching units. Unless the metallic parts, however, are kept at the same potential, intermittent contact or even varying pressure between such parts causes noise in the output radio circuit. Heretofore it has been the practice to produce an intimate bond between the metallic parts by prick punching or swaging such parts together, thereby preventing relative movement of the parts or variation in the pressure therebetween and keeping the parts at the same potential. But such joining of. metallic parts requires that the parts be cut or forced apart if repair, replacement or salvage of switch parts become necessary.

It is therefore an object of the present invention to so join all the metallic parts of a switch by low resistance bonds as to maintain all such parts at substantially the same potential.

Another object of the present invention is to provide a switch in which all of the metallic parts thereof are intimately bonded, thereby preventing potential variations which cause disturbances in the switched circuits or in adjacent circuits.

Another object of the invention is to provide a switch for electrical circuits in which the bonding between the metallic frame or supports of the switch parts is such that the switch may be disassembled and reassembled without damage to any parts and without disturbing the eflicacy of the bond therebetween.

Objects and advantages of the invention other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig, 1 is a side elevation showing a switch structure including a plurality of switch units and embodying the present invention;

Fig. 2 is an elevation looking in the direction of the arrows II-II in Fig. l of one of the switching units:

Fig. 3 is an elevational view looking in the direction of the arrows III-m in Fig. 1 of one of the switch units Fig. 4 is a fragmentary view partially in vertical section and partially in elevation on the plane of line IVIV of Fig. 1 on an enlarged scale; and

Fig. 5 is a cross-sectional view taken on the plane of the line V--V of Fig, 4 to show the relation of the screws and. spacers.

Referring to the drawing, the reference numeral l0 designates a metallic frame or supporting plate having a bushing ll rigidly mounted thereon. A portion of the bushing is exteriorly threaded, as indicated at l2, for fastening the switch on a panel, a radio chassis or other suitable support, as is well known, and the bushin supports an operating shaft lit for operating the switching units. The shaft is provided with an index mechanism which generally comprises an index wheel l6 having indentations on the periphery thereof engageable with a ball detent l1 mounted in and extending from a socket formed in an arm l8 extending from the supporting plate Ill. The ball I1 is pressed into the wheel indentations by a spring l9 held between the plate l0 and the bushing I l A plurality of screw bolts 22 (refer now to Fig. 4) extend through the supporting plate ill to receive spacer sleeves 23 and ball washers 24 between which are mounted similar switch units generally designated 26 and 21. The switch units are clamped between the spacers and washers by tightening nut 28 against a lock washer 29 to place the spacers, the ball washers, and a portion of the switch units under compression. The spacers 23 and the washers 24 are an easy fit on the bolts 22, as is indicated in Fig. 5, to facilitate assembly and disassembly of the switch.

Each switch unit 26 and 21 includes a fixed or stator plate 3| which is washer-like in form and is made of a suitable insulating material but is preferably a ceramic. The stator plate 3| has enlargements 82, preferably on diametrically opposite points of its periphery, about holes through which the screws 22 pass, the ball surfaces of the washers 24 seating on the edges of the holes in such manner as to minimize the localization of compressive stresses in the plate. The stator plate 31 has suitably mounted thereon, as by eyelets 33, a plurality of clips 34 to the outer ends of which are to be connected the conductors of the various circuits to be controlled by the switch. The clips are preferably of double layer or leaf construction and may be bent at the outer ends into any position desired to facilitate attachment of the circuit conductors thereto. The clips 34 extend into the interior circular space of known.

, The stator plate 31 is formed with a plurality of substantially radial projections 35 extending into the circular space within the plate, the projections defining a circular space within which is mounted a movable switch member. The movable switch member or rotor comprises a plate 31 made of suitable insulating material, but is preferably made of a ceramic material, and is of a size for rotation in the space defined by the stator projections 35. The rotor plate 3''! has mounted on one side thereof a washer-like metallic ring 38 with a contact lug 39 extending beyond the periphery of the ring. A plate 40 of suitable insulating material is mounted on the other side of the rotor plate 31, as by eyelets 4|, which also serve to attach the ring 38 to the plate. The contact ring 38 and the plate 40 each extend beyond the periphery of the rotor plate 31, thus forming a channel into which the stator projections 35 extend to retain the switch rotor in the-plane of the stator' upon movement of the rotor. The shaft 13 has a flattened portion extending through a hole 42 in the switch rotors 40 and simultaneously moving all of the switch rotors upon movement of the shaft. It will be understood that the contact ring 38 moves between the double contacts of the longer stator clips 34 and that the rotor contact lug 39 moves between the double contacts of the shorter stator clips.

In the use of a switch constructed as above described, as for example with-electronic equipment, intermittent contacting or even varying of the pres-sure between the metallic parts, due to vibration, produces variations in the electrical potential of such parts and causes noise in such equipment. Because the switch must be capable of assembly and disassembly, means must be provided which will insure continuous contact between the metallic parts and yet will allow assembly and disassembly of the switch without requiring destruction of any parts thereof. According to the present invention such continuous contact is produced by forming metal bands, indicated at 44, around each of the bolt holes on each side of the stator plates 3| and over the outer edges of the plates between the bolt holes, thus providing a continuous metallic path between the supporting plate l0, spacers 23, washers 24, and bolts 22, which insures keeping of all such parts at the same potential. The bands 44 are preferably coatings of good electrical conductive material, such as silver, and are applied by any of the methods now known in the art in such manner that the bands are bonded or interlocked with insulating plates 3|. The area of the bands is preferably limited to that area which is required to securesuflicient contact surface with the washers 24 to provide a current conductive path to equalize the potential of the metallic parts of the switch. The present construction entirely avoids potential variations in the metallic parts of a switch so that the switch may be used in the most sensitive electronic equipment under adverse conditions without causing noise in such equipment.

Although but one embodiment of the present invention has been illustrated and described, it

will be apparent to those skilled inthe art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

We claim:

1. In a switch comprising a metallic plate and insulating material plates, metallic means joining the metallic and the insulating plates in spaced relation, and means integral with the insulating plates for electrically bonding the metallic plate and the metallic joining means to secure uniform electrical potential thereon.

2. In a switch comprising a metallic plate and insulating material plates, metallic screws extending through the metallic plate and the insulating plates, metallic spacers mounted on the screws between the several plates, means interlocked with the insulating plate for bonding the metallic plate, the screws, and the spacers to provide a continuous path for the equalization of electrical potential thereon.

3. In a switch comprising a metallic plate and insulating material plates, metallic screws extending through the metallic plate and the insulating plates, metallic spacers mounted on the screws between the several plates, and metallic coatings formed on the insulating plates for electrically connecting the spacers to maintain the potential of all of the said metallic parts of the switch at the same value.

4. In a switch comprising a metallic plate and insulating material plates, all of the plates having holes therethrough adjacent the edges thereof, metallic screws extending through the holes, metallic spacers on the screws between the plates, the plates and the spacers being clamped in spaced relation, and metallic coatings bonded on and extending around the holes through the insulating plates and over the edges thereof between the holes to form an electrical bond between the metallic parts and maintain a uniform electrical potential thereon.

ROBERT L. WOLFF. WILLIAM J. FOY.

REFERENCES CITED The following references are of record in the Theory and Application of Electron Tubes, H. J. Reich, 1944, page 196. (Copy in Div. 54.)

Meissner "How to Build Instruction Manual. Copyright 1943 by Meissner Manuf. vCo., Mt. Camel, Ill., pages 131, 132.

Radio Receiver Troubles, Their Cause and Remedy (14X-1), Nat. Radio Inst., 1941 ed., Wash, D. 0., pages 11 and 12, section 3. 

